Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1-1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as β-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using β-hematin, rather than hemozoin, for photoacoustic measurements. We characterized β-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that β-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm(-1). Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the β-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.

中文翻译：

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β-血红素的光声光谱


疟疾每年影响超过 2 亿人，导致 80 万人死亡。目前的检测使用血涂片，只有当 0.1-1% 的血细胞被感染时才能检测到这种疾病。我们正在研究使用光声流量计来检测 1000 万或更多正常血细胞中少至一个受感染的细胞，从而在患者出现症状之前诊断感染。光声流量计与传统的流式细胞术类似，不同之处在于纳秒激光脉冲靶向稀有细胞以诱导超声波响应。该系统已用于检测 10 毫升血液中的单个黑色素瘤细胞。我们的目标是应用光声流量计来检测疟疾色素疟原虫色素，它是血液中寄生虫消化的血红蛋白的副产品。然而，超过一毫克的疟红素很难纯化，因此从猪血红素中提取了一种合成类似物，称为 β-血红素。本研究的具体目的是确定使用 β-血红素（而不是疟原虫色素）进行光声测量的功效。我们使用紫外可见光谱、TEM 和 FTIR 表征了 β-血红素，然后测试了激光照射对合成产品的影响。我们最终使用光声激发确定了其吸收光谱。紫外可见光谱证实β-血红素与其前体明显不同。 TEM 分析证实了其先前确定的纳米棒形状，并将 FTIR 结果与已发表的光谱数据进行比较表明，我们的产品在 1661 和 1206 cm(-1) 处具有独特的吸收峰。此外，我们的研究表明，长时间的照射会显着改变 β-血红素的物理和光学特性，导致较短波长的吸收增加。 尽管如此，光声吸收光谱模仿了紫外可见光谱产生的光谱，这证实了光声方法的准确性，并强烈表明光声流量计可以用作诊断疟疾感染的工具。